testing cya

[l1tech]

Being that cya takes so long to dissolve how long should one wait after adding it to test the water?

[Watermom]

To be sure it is all dissolved, it is best to wait about a week.

[l1tech]

Wow...I was thinking more like a couple of days but I am sticking with your answer.

[steveinaz]

To be sure it is all dissolved, it is best to wait about a week.

I agree. After I added CYA, I checked 4 days later and I got 40ppm. A week later I checked again and read 55-60ppm. I think it takes the stuff a good while to totally dissolve.

[chem geek]

If you want (in the future) to dissolve CYA more quickly, take a look at this post for some options.

Richard

[ehorn]

Well I'm not sure if this is good practice or not but the guy who started up our pool poured the CYA in the skimmer so that it would be feed into the filter. He said it would disolve the fastest in there. I never tested for CYA so I have no idea how long it actually took to disolve into the water. I'm assuming it would have been fast if it had the volume of water flowing past it through the filter all the time.

Has anyone heard of this as a good way to add CYA?

Eric

[Watermom]

That is the way I always add CYA - directly into the skimmer. Works fine.

In the thread ChemGeek referenced it states:
1) Put CYA into panty hose and have it hang over the side of your pool over a return. That's PatL's idea and people swear by it. Dissolves in about 24 hours.

I can't imagine how that would make any difference. Hanging over the side in front of the return is water running over it. Having it in the filter -- is also having water continuously washing over it. Seems to me there shouldn't be any difference then in the amount of time these two methods dissolve it.

[chem geek]

The only difference I can think of is that with the pantyhose technique, the water flow per area of CYA exposed to it is VERY high -- perhaps around 15 GPM or so. In the filter, there is a lot of area so the CYA probably spreads out a bit and the flow rate is much slower since the 45 GPM or so total flow is spread out over the entire filter area.

I'm really just guessing, but PatL and followers of that technique swear by it as dissolving very quickly (i.e. 24 hours) while the skimmer to filter technique is know to still take many days to fully dissolve.

If the CYA was kept fully in the skimmer until it completely dissolved, then the probably 15 GPM flow rate through the skimmer would be equivalent to the return. However, unless you use a material to hold the CYA that has roughly the same filtering size as the filter, then whatever gets through that is bigger will end up stuck in the filter and subject to the lower flow rate.

Richard

[JohnT]

The downside to putting it directly into the skimmer is that if you backwash before it is dissolved, you lose some of the CYA. There is a wide variation in the time it takes CYA to dissolve. In my pool, it is gone from a sock overnight. Others report much longer times.